ref: bf8577992e69de9182d29fe37739dbd6b5ac7354
dir: /src_common/SKP_Silk_HP_variable_cutoff.c/
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#include "SKP_Silk_main_FIX.h"
#include "SKP_Silk_tuning_parameters.h"
#define SKP_RADIANS_CONSTANT_Q19 1482 // 0.45f * 2.0f * 3.14159265359 / 1000
#define SKP_LOG2_VARIABLE_HP_MIN_FREQ_Q7 809 // log(80) in Q7
/* High-pass filter with cutoff frequency adaptation based on pitch lag statistics */
void SKP_Silk_HP_variable_cutoff(
SKP_Silk_encoder_state *psEncC, /* I/O Encoder state */
SKP_int16 *out, /* O high-pass filtered output signal */
const SKP_int16 *in, /* I input signal */
const SKP_int frame_length /* I length of input */
)
{
SKP_int quality_Q15;
SKP_float pitch_freq_low_Hz;
SKP_int32 B_Q28[ 3 ], A_Q28[ 2 ];
SKP_int32 Fc_Q19, r_Q28, r_Q22;
SKP_int32 pitch_freq_Hz_Q16, pitch_freq_log_Q7, delta_freq_Q7;
/*********************************************/
/* Estimate Low End of Pitch Frequency Range */
/*********************************************/
if( psEncC->prevSignalType == TYPE_VOICED ) {
/* difference, in log domain */
pitch_freq_Hz_Q16 = SKP_DIV32_16( SKP_LSHIFT( SKP_MUL( psEncC->fs_kHz, 1000 ), 16 ), psEncC->prevLag );
pitch_freq_log_Q7 = SKP_Silk_lin2log( pitch_freq_Hz_Q16 ) - ( 16 << 7 ); //0x70
/* adjustment based on quality */
quality_Q15 = psEncC->input_quality_bands_Q15[ 0 ];
pitch_freq_log_Q7 = SKP_SUB32( pitch_freq_log_Q7, SKP_SMULWB( SKP_SMULWB( SKP_LSHIFT( quality_Q15, 2 ), quality_Q15 ),
pitch_freq_log_Q7 - SKP_LOG2_VARIABLE_HP_MIN_FREQ_Q7 ) );
pitch_freq_log_Q7 = SKP_ADD32( pitch_freq_log_Q7, SKP_RSHIFT( SKP_FIX_CONST( 0.6, 15 ) - quality_Q15, 9 ) );
//delta_freq = pitch_freq_log - psEnc->variable_HP_smth1;
delta_freq_Q7 = pitch_freq_log_Q7 - SKP_RSHIFT( psEncC->variable_HP_smth1_Q15, 8 );
if( delta_freq_Q7 < 0 ) {
/* less smoothing for decreasing pitch frequency, to track something close to the minimum */
delta_freq_Q7 = SKP_MUL( delta_freq_Q7, 3 );
}
/* limit delta, to reduce impact of outliers */
delta_freq_Q7 = SKP_LIMIT_32( delta_freq_Q7, -SKP_FIX_CONST( VARIABLE_HP_MAX_DELTA_FREQ, 7 ), SKP_FIX_CONST( VARIABLE_HP_MAX_DELTA_FREQ, 7 ) );
/* update smoother */
psEncC->variable_HP_smth1_Q15 = SKP_SMLAWB( psEncC->variable_HP_smth1_Q15,
SKP_MUL( SKP_LSHIFT( psEncC->speech_activity_Q8, 1 ), delta_freq_Q7 ), SKP_FIX_CONST( VARIABLE_HP_SMTH_COEF1, 16 ) );
}
/* second smoother */
psEncC->variable_HP_smth2_Q15 = SKP_SMLAWB( psEncC->variable_HP_smth2_Q15,
psEncC->variable_HP_smth1_Q15 - psEncC->variable_HP_smth2_Q15, SKP_FIX_CONST( VARIABLE_HP_SMTH_COEF2, 16 ) );
/* convert from log scale to Hertz */
pitch_freq_low_Hz = SKP_Silk_log2lin( SKP_RSHIFT( psEncC->variable_HP_smth2_Q15, 8 ) );
/* limit frequency range */
pitch_freq_low_Hz = SKP_LIMIT_32( pitch_freq_low_Hz, SKP_FIX_CONST( VARIABLE_HP_MIN_FREQ, 0 ), SKP_FIX_CONST( VARIABLE_HP_MAX_FREQ, 0 ) );
/********************************/
/* Compute Filter Coefficients */
/********************************/
/* compute cut-off frequency, in radians */
//Fc_num = (SKP_float)( 0.45f * 2.0f * 3.14159265359 * pitch_freq_low_Hz );
//Fc_denom = (SKP_float)( 1e3f * psEncC->fs_kHz );
SKP_assert( pitch_freq_low_Hz <= SKP_int32_MAX / SKP_RADIANS_CONSTANT_Q19 );
Fc_Q19 = SKP_DIV32_16( SKP_SMULBB( SKP_RADIANS_CONSTANT_Q19, pitch_freq_low_Hz ), psEncC->fs_kHz ); // range: 3704 - 27787, 11-15 bits
SKP_assert( Fc_Q19 >= 3704 );
SKP_assert( Fc_Q19 <= 27787 );
r_Q28 = SKP_FIX_CONST( 1.0, 28 ) - SKP_MUL( SKP_FIX_CONST( 0.92, 9 ), Fc_Q19 );
SKP_assert( r_Q28 >= 255347779 );
SKP_assert( r_Q28 <= 266690872 );
/* b = r * [ 1; -2; 1 ]; */
/* a = [ 1; -2 * r * ( 1 - 0.5 * Fc^2 ); r^2 ]; */
B_Q28[ 0 ] = r_Q28;
B_Q28[ 1 ] = SKP_LSHIFT( -r_Q28, 1 );
B_Q28[ 2 ] = r_Q28;
// -r * ( 2 - Fc * Fc );
r_Q22 = SKP_RSHIFT( r_Q28, 6 );
A_Q28[ 0 ] = SKP_SMULWW( r_Q22, SKP_SMULWW( Fc_Q19, Fc_Q19 ) - SKP_FIX_CONST( 2.0, 22 ) );
A_Q28[ 1 ] = SKP_SMULWW( r_Q22, r_Q22 );
/********************************/
/* High-Pass Filter */
/********************************/
SKP_Silk_biquad_alt( in, B_Q28, A_Q28, psEncC->In_HP_State, out, frame_length );
}